This invention relates generally to communication systems and, more particularly, to a technique of broadcasting network timing 5 information and identification numbers to remote units (RUs) in a wireless communication network.
Some communications are synchronously timed, so that base stations and remote units are both operating in response to precision clocks. Then, overhead can be saved by organizing communication so that units use pre-assigned time slots. However, synchronized communications require that the remote units to be equipped with precision clocks, to be supplied with frequent timing corrections, or both. To this end, global positioning satellite (GPS) receivers are often used to access precision satellite timing. GPS receivers cannot be conveniently used in all situations. However, when they, or some other precision timing element, are attached to the remote units, events can be recorded with respect to a network clock, or time-stamped. That is, both the base stations and remote units are able to reference events against a common defined measure of absolute time. This time-stamp information makes billing and maintenance events easier to accomplish.
Multiple access wireless communication networks, including first, second, and third generation cellular telephones, are typically organized around a centralized set of protocols which are maintained and initialized from a central site such as a mobile switching center (MSC). The MSC organizes the flow of communications between base stations (BSs) and remote units (RUs). These multiple access networks are typically asynchronous, meaning the communications are organized in a framing structure that depends on the remote units adopting the timing of the base station and responding to base station commands which are embedded in control channels. Many multiple access networks, such as GSM, TDMA (time division multiple access), and the AT&T fixed wireless OFDM (orthogonal frequency division multiplexed) systems break communication frames into time slots, where various units in the network are assigned time slots for the receipt and transmission of information. There are many prior art systems for coarse and fine acquisition of the network time slots, framing structure, and frequencies so that the timing of remote units can be synchronized to the base station, and ultimately the MSC. However, even when synchronized these remote units still have no absolute time information, and events cannot be accurately time-stamped from the point of view of the remote units, unless traffic channel resources are allocated for communications which mark special events or the remote units are equipped with precision clocks.
It would be advantageous if events could be time-stamped at remote units in a multiple access communications network without establishing a synchronous framing protocol, without equipping the remote units with precision clocks, or without the overhead of requesting and receiving timing markers from the MSC.